Osteoarthritis (OA), diagnosed in over 15% of the US population, is the primary cause of musculoskeletal lower extremity disability. Although there is no cure, exercise remains the core treatment to manage OA regardless of age, comorbidity, pain, severity or disability. Yet, many people with this condition do not engage in regular fitness and thus may resort to invasive and risky joint replacement surgeries due to pain and decreased mobility, or they may experience health decline due to sedentary lifestyles. The goal of this Phase I STTR proposal is to complete the design, safety and usability testing of AFARI(tm), for use by individuals diagnosed with lower extremity OA. Created to fill an unmet need for populations who without adequate mobility support would be less likely, fully unable, or unwilling to participate in ambulatory exercise, AFARI is a three-wheeled device, and provides the mechanisms to unload body weight. AFARI was created to promote participation in outdoor walking, jogging, or running. Although durable medical equipment (DME) such as walkers, crutches and canes is available to those who need it, DME is minimally functional for outdoor exercise, and is often perceived as stigmatizing and inconvenient. Therefore, many people with lower-extremity OA abandon these devices. AFARI was designed to mitigate abandonment and eliminate a number of barriers to regular outdoor fitness activity by persons with lower-extremity OA. AFARI will allow the user to safely and successfully initiate, maintain, and/or increase the length and intensity of their exercise programs. In preliminary market research for AFARI, respondents indicated that form was as important as function and ease of use if they were to adopt AFARI and the device was designed with these principles in mind. Through this STTR effort, several major barriers to timely commercialization of AFARI will be researched so that they can be eliminated. The safety and stability of AFARI will be proven though mechanical testing and human evaluation. The weight bearing monitoring system will be concurrently validated against bodily weight bearing measures. An evaluation of the reduction in fall risk tested by fear of falling will be undertaken; Data on usability, destigmatizing design, and overall desirability of AFARI will be collected, and, tasks will be planned to educate clinicians regarding AFARI and its benefits. To accomplish the objective of this Phase I study, to demonstrate the initial feasibility of AFARI for people with lower extremity OA, such that we can proceed with expanded efforts in Phase II, four specific aims will be met: AIM 1) Validation of the functionalit and safety of AFARI; AIM 2) Concurrent validation of the weight bearing monitoring system; AIM 3) Conducting preliminary usability testing focusing on comfort, function, convenience, stigma reduction, and design preferences, and AIM 4) Planning for clinician education about AFARI.